The present invention relates to a method of vaccinating domesticated birds against coccidiosis. In particular, the invention relates to the in ovo administration of live Eimeria spp sporocysts or oocysts, or mixtures thereof, into the developing eggs of domesticated birds in order to immunize the hatched chicks against coccidiosis.
Coccidiosis is an enteric disease of domesticated birds caused by infection with intracellular protozoan parasites of the genus Eimeria. Coccidiosis is the most economically devastating parasitic disease of domesticated birds. It is estimated that anticoccidial medications and losses due to coccidiosis cost the poultry industry hundreds of millions of dollars every year.
Various attempts to vaccinate domesticated birds against coccidiosis have been reported since the early 1950""s. Current vaccination methods include administering live Eimeria oocysts to birds through feed or water. These methods, however, are inconvenient and inefficient because not all birds get the intended oocyst dose and many are either unprotected by the vaccine or receive a pathogenic infection.
In J. M. Sharma and B. R. Burmester, Avian Dis. 26: 134-149, 1981, the authors reported that chickens vaccinated in ovo with herpesvirus of turkey developed immunity against subsequent challenge with Marek""s disease virus. In European patent publication no. 291173, an immunization process is referred to wherein a nonreplicating immunogen is administered in ovo. The immunogens specifically referred to in the European patent are a genetically engineered Eimeria antigen and an Eimeria oocyst extract. The European patent specifically excludes live parasite stages such as those used in the vaccination method claimed herein.
The present vaccination method involves in ovo administration of live Eimeria sporocysts or oocysts, or a mixture thereof, into the developing eggs of domesticated birds. The available literature suggests that such a vaccination method would be ineffective in ovo and should be applied post-hatch. In T. K. Jeffers and G. E. Wagenbach, J. Parasit. 56(4): 656-662, 1970, the authors reported that in ovo injection of E. tenella sporozoites on day 10 of incubation provided no significant immunological protection against subsequent challenge with E. tenella oocysts. In fact, they reported that chicks that received no treatment had a greater survival rate against subsequent challenge with E. tenella oocysts than chicks that had been treated in ovo with sporozoites. In K. L. Watkins et al., Proc. VI th. International Coccidiosis Conf., Abstract E1-2, Ontario, Canada, 1993, the authors described in ovo inoculation with live E. maxima sporocysts and sporulated oocysts, although they did not indicate when the inoculation was done during incubation of the egg. Watkins et al. concluded that their study provided no evidence that in ovo exposure protects against subsequent coccidial challenge with E. maxima oocysts 10 days post-hatch. They also concluded that significant immunological protection is provided if inoculation is done soon after hatch rather than in ovo. Contrary to this teaching, the in ovo vaccination method of the present invention provides unexpected immunity that protects the hatched birds against subsequent coccidial challenge.
The present invention, also referred to herein as the xe2x80x9cpresent vaccination methodxe2x80x9d, relates to a method of vaccinating a domesticated bird against coccidiosis comprising administering in ovo, during the final quarter of incubation, an effective immunizing dose of live Eimeria sporocysts or oocysts, or a mixture thereof.
The term xe2x80x9cdomesticated bird(s)xe2x80x9d, as used herein, unless otherwise indicated, includes chickens, turkeys, ducks, game birds (including, but not limited to, quail, pheasants, and geese) and ratites (including, but not limited to, ostrich).
The term xe2x80x9cin ovoxe2x80x9d, as used herein, unless otherwise indicated, means into a domesticated bird egg containing a live, developing embryo.
The term xe2x80x9cadministering in ovoxe2x80x9d or xe2x80x9cin ovo administrationxe2x80x9d, as used herein, unless otherwise indicated, means administering the vaccine described herein to a domesticated bird egg containing a live, developing embryo by any means of penetrating the shell of the egg and introducing the vaccine. Such means of administration include, but are not limited to, injection of the vaccine.
The term xe2x80x9cfinal quarter of incubationxe2x80x9d, as used herein, unless otherwise indicated, means the final quarter of incubation of a developing egg of a domesticated bird.
The term xe2x80x9cEimeriaxe2x80x9d, as used herein, unless otherwise indicated, means one or more species of the genus Eimeria that infect domesticated birds. Such Eimeria species include those that are found in chicken, including E. tenella, E. acervulina, E. maxima, E. necatrix, E. mitis, E. praecox, and E. brunetti, and also those that are found in turkeys, including E. meleagrimitis, E. adenoeides, E. gallopavonis, E. dispersa, E. meleagridis, E. innocua, and E. subrotunda, and also Eimeria species that infect other domesticated birds as defined above. The term xe2x80x9cEimeriaxe2x80x9d also includes all strains of the foregoing species of Eimeria, including, but not limited to, precocious strains, and attenuated strains, which includes strains that have been irradiated, or otherwise treated, so that they fail to complete development. The term Eimeria also includes any newly-discovered strains or species of Eimeria that infect domesticated birds as defined above.
The term xe2x80x9csporocystsxe2x80x9d, as used herein, unless otherwise indicated, means live Eimeria sporocysts.
The term xe2x80x9coocystsxe2x80x9d, as used herein, unless otherwise indicated, means live Eimeria sporulated oocysts or a mixture of sporulated and unsporulated oocysts.
The term xe2x80x9ceffective immunizing dosexe2x80x9d, as used herein, unless otherwise indicated, means a number of sporocysts or oocysts, or, when mixed, a number of sporocysts and oocysts, sufficient to provide immunological protection in the hatched birds that is greater than the inherent immunity of non-immunized birds. As used herein, the terms xe2x80x9cimmunizexe2x80x9d and xe2x80x9cvaccinatexe2x80x9d are synonymous and are used interchangeably.
A preferred dose to be administered in accord with the method of the invention comprises 102 to 108 sporocysts or oocysts, or a mixture thereof wherein the total number of said sporocysts and oocysts ranges from 102 to 108.
A more preferred dose comprises 102 to 105 sporocysts or oocysts, or a mixture thereof wherein the total number of said sporocysts and oocysts ranges from 102 to 105.
Another preferred dose comprises 105 to 107 sporocysts or oocysts, or a mixture thereof wherein the total number of said sporocysts and oocysts ranges from 105 to 107.
Another preferred dose comprises 104 to 105 sporocysts or oocysts, or a mixture thereof wherein the total number of said sporocysts and oocysts ranges from 104 to 108.
Another preferred dose comprises 103 to 106 sporocysts or oocysts, or a mixture thereof wherein the total number of said sporocysts and oocysts ranges from 103 to 106.
A preferred domesticated bird to be vaccinated in accord with the method of the invention is a chicken.
A preferred dose to be administered in ovo to chicken eggs comprises sporocysts or oocysts, or a mixture thereof, of two or more species of Eimeria selected from the group consisting of E. tenella, E. acervulina, E. maxima, E. necatrix, E. mitis, E. praecox, and E. brunetti. 
Another preferred domesticated bird to be vaccinated in accord with the method of the invention is a turkey.
A preferred dose to be administered in ovo to turkey eggs comprises sporocysts or oocysts, or a mixture thereof, of two or more species of Eimeria selected from the group consisting of E. meleagrimitis, E. adenoeides, E. gallopavonis, E. dispersa, E. meleagridis, E. innocua, and E. subrotunda. 
Other preferred domesticated birds to be vaccinated in accord with the method of the invention are game birds, ducks and ratites.
The method of the invention further comprises, in combination with the present vaccination method, administering in ovo an immune stimulant at any time during incubation.
A preferred method of administering the immune stimulant is simultaneously with the in ovo administration of a dose of sporocysts or oocysts, or mixture of said sporocysts and oocysts, during the final quarter of incubation.